Performance Analysis for STAR-RIS-Assisted Wireless Powered Communications With Cooperative Jamming

This article investigates the simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) assisted secure transmissions in wireless powered communication (WPC) systems. According to the conditions of communication links, three scenarios are considered. Correspondingly, two transmission schemes are proposed for outdoor and indoor users to enhance the reliability and security of the communication system in each scenario. To be specific, for the scenario-I with blocked energy harvesting links, the scenario-I based information transmission of outdoor-user and cooperative jamming of indoor-user (IbTOJI) scheme, and cooperative jamming of outdoor-user and information transmission of indoor-user (IbJOTI) scheme are proposed, respectively. For the scenario-II with blocked information transmission (IT) links, scenario-II-based IT of outdoor-user and cooperative jamming of indoor-user (IIbTOJI) scheme, and cooperative jamming of outdoor-user and IT of indoor-user (IIbJOTI) scheme are proposed, respectively. For the scenario-III which deploys a hybrid access point (HAP), the direct links of the energy harvesting and IT are blocked. Scenario-III-based IT of outdoor-user and cooperative jamming of indoor-user (IIIbTOJI) scheme, and cooperative jamming of outdoor-user and IT of indoor-user (IIIbJOTI) scheme are proposed, respectively. We analyze the closed-form expressions of outage probability and intercept probability for each scheme. The result shows that IIIbTOJI scheme has the best reliable performance among the proposed schemes, and IbJOTI and IIIbJOTI schemes perform best in security.